"T" "C" "S" are all sibilant sounds, as I said in a link above the hard areas for an with the Summits are 5khz to 20khz (the sibilance area) and again 3.5khz (presence area of the mids).
And the Prima Luna has a very odd high frequency boost in the top end which I believe to be output transformer oscillation which could very well exaggerate "sibilance".
https://www.stereophile.com/images/1214PLDPIfig01.jpg
Cheers George
And the Prima Luna has a very odd high frequency boost in the top end which I believe to be output transformer oscillation which could very well exaggerate "sibilance".
https://www.stereophile.com/images/1214PLDPIfig01.jpg
Cheers George